1. Field of the Invention
Exemplary embodiments of the present invention relate to a harmonic rejection mixer and a harmonic rejection mixing method, and more particularly, to a mixing method and apparatus for generating a plurality of oscillator signals having ⅓ duty cycles and uniform phase differences and rejecting harmonics by using the oscillator signals.
2. Description of the Related Art
As signals of undesired channels are input to a receiver of a broadband wireless communication system, and more particularly, a wireless broadcasting communication system such as an Advanced Television Systems Committee (ATSC) system, these signals may be combined with harmonics of a local oscillator (LO) of the receiver and added to a desired channel during a frequency mixing process. The added signals may act as noise and may reduce a signal-to-noise ratio (SNR) of the receiver.
Methods of reducing harmonic mixing in a broadband receiver may include a method using a radio frequency (RF) filter and a method using a frequency mixer. The RF filter method may simply reject harmonics by using only one filter but may have to use an external element to obtain a desired level of harmonic rejection in consideration of the performance of a system. Meanwhile, the frequency mixer method may combine multi-phase LO signals with an input signal by using a plurality of parallel frequency mixers and may remove an effect due to harmonic mixing by adjusting gains of combined signals. Although this method may realize an on-chip device, LO signals having uniform phase differences may not be easily formed over a broadband and harmonic rejection may be reduced due to mismatches between parallel circuits. A method of dividing a high frequency LO signal may be used to form uniform phase differences over a broadband. However, this method may have a high structural complexity and may increase power consumption.
Accordingly, a frequency mixer rejecting harmonics, with low power consumption may be required.